The present invention relates to a power semiconductor device and more particularly to a semiconductor device having a function of detecting a current.
Current detection has been eagerly demanded in the application of the power semiconductor device. The current flowing through the semiconductor device is detected to carry out several controls such as excess current detection for device protection, constant current control, etc. There have been proposed, as a technique for current detection, (1) a method for measuring a voltage across a resistor externally provided in series with a power semiconductor device, and (2) a method of detecting a shunting current (e.g. about 1/1000) of the current flowing through a power MOS transistor using an externally provided resistor, which is disclosed in U.S. Pat. No. 4,553,084.
However, both of the methods mentioned above have the following disadvantages. The method (1) has disadvantages of serious loss due to the externally provided resistor and necessity thereof. The method (2) can relax the loss due to the externally provided resistor as compared with the method (1) since the shunting current is detected, but still has disadvantages of being substantially limited, as the power semi-conductor device, to a power MOS transistor in relation to the shunting ratio, and also of necessity of the externally provided resistor. The externally provided resistor should have a small resistance value in order to reduce the loss, and in the contrary, should have a large resistance value in order to eliminate variations in resistance due to its connection to realize the enhanced detection accuracy. It is impossible to simultaneously satisfy both requirements since they are contradictory. In recent years, there has been a tendency of constructing a circuit of controlling a high power in an IC (referred to a power IC or intelligent power IC). The externally provided resistor disadvantageously goes against such a tendency.